The carob (Ceratonia siliqua) is a flowering evergreen tree or shrub in the legume family, Fabaceae. In English, it is also known as “St John’s bread”, as well as “locust tree”,(not African locust bean) the designation also applied to several other trees from the same family. It is widely cultivated for its edible pods, and as an ornamental tree in gardens and landscapes. The carob tree is native to the Mediterranean region and the Middle East.
The word “carob” comes from Middle French carobe (modern French caroube), which has it roots in the Arabic خَرُّوبٌ (kharrūb, “locust bean pod”), ultimately perhaps from Akkadian language ‘kharubu’ or Aramaic ‘kharubha’, related to Hebrew ‘harubh’. Ceratonia siliqua, the scientific name of the carob tree, derives from the Greek κεράτιον (kerátiοn), “fruit of the carob” (from keras κέρας “horn”), and Latin siliqua “pod, carob”. The unit “carat”, used for weighing precious metal and stones, also comes from κεράτιον, as alluding to an ancient practice of weighing gold and gemstones against the seeds of the carob tree by people in the Middle East. The system was eventually standardized, and one carat was fixed at 0.2 gram. In late Roman times, the pure gold coin known as the solidus weighed 24 carob seeds (about 4.5 grams). As a result, the carat also became a measure of purity for gold. Thus, 24-carat gold means 100% pure, 12-carat gold means the alloy contains 50% gold.
The carob tree grows up to 15 m (49 ft) tall. The crown is broad and semispherical, supported by a thick trunk with rough brown bark and sturdy branches. Its leaves are 10 to 20 cm (3.9 to 7.9 inch) long, alternate, pinnate, and may or may not have a terminal leaflet. It is frost-tolerant to roughly −7°C (20 °F).
Most carob trees are dioecious and some are hermaphroditic, so strictly male trees do not produce fruit. When the tree blossoms in autumn, the flowers are small and numerous, spirally arranged along the inflorescence axis in catkin-like racemes borne on spurs from old wood and even on the trunk (cauliflory); they are pollinated by both wind and insects. The male flowers smell like human semen, an odor that is caused in part by amines.
The fruit is a legume (also known commonly, but less accurately, as a pod), that is elongated, compressed, straight, or curved, and thickened at the sutures. The pods take a full year to develop and ripen. When the sweet ripe pods eventually fall to the ground, they are eaten by various mammals, such as swine. The ripe, dried, and sometimes toasted pod is often ground into carob powder, which is sometimes used to replace cocoa powder. Carob bars (an alternative to chocolate bars), as well as carob chips (an alternative to chocolate chips), and carob treats are often available in health food stores. Carob pods are naturally sweet, not bitter, and contain no theobromine or caffeine.
Although cultivated extensively, carob can still be found growing wild in eastern Mediterranean regions, and has become naturalised in the west. The tree is typical in the southern Portuguese region of the Algarve, where the tree is called alfarrobeira, and the fruit alfarroba. It is also seen in southern and eastern Spain (Spanish: algarrobo, algarroba), mainly in the regions of Andalusia, Murcia and Valencia (Valencian: garrofer, garrofa); Malta (Maltese: ħarruba), on the Italian islands of Sicily (Sicilian: carrua) and Sardinia (Italian: carrubo, carruba), in Southern Croatia (Croatian: rogač), in eastern Bulgaria (Bulgarian: рожков), and in Southern Greece, Cyprus, as well as on many Greek islands such as Crete and Samos. The common Greek name is χαρουπιά (translit. charoupia), or ξυλοκερατιά (translit. ksilokeratia, meaning “wooden horn”). In Turkey, it is known as “goat’s horn” (Turkish: keçiboynuzu). The various trees known as algarrobo in Latin America (Albizia saman in Cuba, Prosopis pallida in Peru and four species of Prosopis in Argentina and Paraguay) belong to a different subfamily, Mimosoideae of the Fabaceae. Early Spanish settlers named them algarrobo after the carob tree because they also produce pods with sweet pulp.